This invention relates to viral proteins and glycoproteins, to compositions containing these proteins, to methods of preparing the proteins, and to their use in detecting viral infection.
The etiological agent of acquired immunodeficiency syndrome (AIDS) is the retrovirus referred to as human immunodeficiency virus (HIV) (Montagnier et al., 1984). To date, two related but distinct viruses, HIV-1 and HIV-2, have been identified (Barre-Sinoussi et al., 1983; Popovic et al., 1984; Levy et al., 1984; Wain-Hobson et al., 1985a; Clavel et al., 1986a; Brun-Vezinet et al., 1987; Guyader et al., 1987). HIV-2 is closely related to simian immunodeficiency virus (SIV), which causes an AIDS-like disease in macaques (Daniel et al, 1985; Sonigo et al., 1985; Chakrabarti et al., 1987).
HIV-1, HIV-2, and SIV show all the features of retrovirus family members (Wain-Hobson et al., 1985b; Montagnier and Alizon, 1987; Guyader et al., 1987; Chakrabarti et al., 1987). Their proviral genomes contain two long terminal repeats (LTRs) and three essential genes required for virus replication encoding the viral internal structural proteins (gag), the reverse transcriptase (pol), and the envelope glycoproteins (env) of the virus. In addition to these genes, both HIVs and SIV contain additional genes encoding the proteins that regulate viral expression (tat and art/trs) and three other genes encoding proteins of unknown function (Q or sor, F or 3′orf, and R). The only notable difference in the genetic organizations of HIV-1, HIV-2, and SIV resides in the open reading frame referred to as X, which is absent in HIV-1.
Alignments of the nucleotide sequences of HIV-1, HIV-2, and SIV reveal a considerable homology between HIV-2 and SIV. These two viruses share about 75% overall nucleotide sequence homology, but both of them are only distantly related to HIV-1 with about 40% overall homology (Guyader et al., 1987; Chakrabarti et al., 1987). At the protein level, the gag and pol proteins of HIV-1, HIV-2, and SIV are antigenically cross-reactive, whereas env proteins are cross-reactive only between HIV-2 and SIV (Clavel et al., 1986b, 1987).
HIV-1, HIV-2, and SIV are both tropic and cytopathic for CD4 positive T lymphocytes (Dagleish et al., 1984; Klatzman et al., 1984; McDougal et al., 1985; Clavel et al., 1986b, 1987; Kannagi et al., 1985; Fultz et al., 1986). A great number of studies have indicated that CD4 functions as the cellular receptor for HIV-1 (for references see Weiss, 1988).
The HIV-1 env gene codes for a 160 Kd glycoprotein that is proteolytically cleaved to yield the extracellular and transmembrane proteins, gp120 and gp41, respectively (Montagnier et al., 1985). It has been demonstrated that HIV-1 recognition of CD4 is mediated by gp120. This complex gp120-CD4 can be identified by co-immunoprecipitation using antibodies specific for the CD4 antigen (McDougal et al., 1986). Following the binding of gp120 to CD4, the entry of HIV-1 into the cell might occur by viral envelope cell membrane fusion (Lifson et al., 1986; Sodroski et al., 1986; Stein et al., 1987; McClure et al., 1988). A putative fusogenic domain in gp41 (Kowalski et al., 1987), which has a sequence homologous to other fusion peptides (Phe-Leu-Gly; Gallaher, 1987), might provide at least one HIV fusion site necessary for this process (Marsh and Dalgleish, 1988).
In the case of HIV-2, a high molecular weight protein of about 130 Kd to about 140 Kd has been associated with the major envelope glycoprotein (Clavel et al., Science, 233: 343-346, 1986). Another glycoprotein having a molecular weight of 120 Kd has been associated with the external glycoprotein of HIV-2 (Guyader et al., Nature, 362: 662-669, 1987). Nevertheless, detailed information for HIV-2 envelope proteins and glycoproteins and their cleavage products and precursors is lacking.
There exists a need in the art for additional information on the structure and in vivo processing of HIV-2 proteins, and especially HIV-2 envelope proteins and glycoproteins. Such information would aid in identifying HIV-2 infection in individuals. In addition, such findings could aid in elucidating the mechanism by which HIV-2 infection and virus proliferation occur and thereby make it possible to devise modes of intervening in viral processes.